DepEd-NSTIC
I. COMPOUND MICROSCOPE
1
The microscope is one of the most expensive apparatuses in a science laboratory. Therefore, extra
care should be taken when using this equipment. One must be familiar with the parts and functions of
the microscope in order to undertake the proper troubleshooting and maintenance procedures
mentioned in this manual.
1*
2*
8*
4*
9*
3*
5*
7*
12*
6*
10*
11*
13*
Figure 1-A. Compound Microscope
Table 1-A. MAJOR PARTS OF A COMPOUND MICROSCOPE
*ITEM
NO.
1
COMPONENT
Eyepiece
2
Body Tube
3
Objectives
4
Revolving Nosepiece
5
Stage
FUNCTION
The eyepiece or oculars are secondary lenses to view an object
with a magnification of 10x in a microscope. Some microscopes
have an eyepiece with a pointer inside.
The body tube supports the eyepiece and the main optical
components of the microscope.
The objectives are the primary lenses of a compound microscope
which are used to magnify images of the specimen. Usually, there
are 3 objective lenses of different powers in a compound
microscope. Their magnification ranges from 4x to 100x and are
labeled on their sides.
The revolving nosepiece is a turret where the objectives are
mounted. When switching from one objective to another, simply
rotate the revolving nosepiece.
The stage is the platform where the slide to be viewed is placed.
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6
Stage Clip
The stage clip keeps the slide in place.
7
Arm
The arm supports the body tube and connects it to the base.
8
Coarse Adjustment Knob
9
Fine Adjustment Knob
10
Tilt Joint
11
Mirror
12
Diaphragm
13
Base
The coarse adjustment knob is the first step for focusing and
scanning of the specimen.
The fine adjustment knob is used for fine focusing, so as to get a
clearer view of the specimen.
The tilt joint allows the user to incline the upper portion of the
microscope to facilitate viewing of the specimen.
The mirror reflects light from a source up through the stage and
to the specimen.
The diaphragm is a rotating disc located below the stage. It is used
to control the amount of light reaching the specimen.
The base is the bottom part which supports the whole unit.
A. PROPER HANDLING
1. Always lift the microscope with two hands: one hand holding the arm, the other hand
supporting the base.
Figure 1-B. Proper way of carrying the microscope
2. Avoid touching the lenses and mirror with bare hands to prevent smearing.
Figure 1-C. Proper way of adjusting the mirror
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B. MAINTENANCE
1. REGULAR CLEANING OF THE UNIT
Clean the equipment regularly. Clean not only the optical components, but also their external
parts. These parts may be stained by grease, dust, and dirt which enhance the growth of fungi.
Materials such as clean rags or tissue paper may be used in cleaning.
Table 1-B. CLEANING OF A MICROSCOPE
With Box / Plastic Cover /
Storage Cabinet
Component
.
1. Eyepiece lenses
No Storage Facility
Clean once a week
Clean twice a week
2. Objective lenses
Clean once a month
Clean twice a month
3. Mirror
Clean once a week
Clean twice a week
4. External components
Clean once a week
Clean twice a week
2. CLEANING THE LENS
To clean the lenses, gently wipe the surfaces with tissue paper or cotton buds. The lenses can
be easily contaminated with eyelashes, fingerprints and specimen, leaving marks on the lens.
Detailed instructions on the thorough cleaning of lenses are provided in the repair section on
page 60 of this manual.
C. STORAGE
Proper storage should be observed. Protect the microscope from dust and fungi by (a) storing it
inside a wooden box or (b) cover it with plastic. Better yet, (c) place the apparatus inside a storage
cabinet when not in use as shown in Figure 1-D. Place silica gel in the wooden box or cabinet to
absorb moisture.
a
b
c
Figure 1- D. Illustrations on proper microscope
storage
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D. TROUBLESHOOTING AND REPAIR
The following tools and materials are needed in cleaning and repairing a microscope:
Table 1-C. TOOLS AND MATERIALS NEEDED FOR CLEANING AND REPAIRING
TOOLS
MATERIALS
•
8” Flat screwdriver
•
Precision screwdrivers
•
Scissors
•
1” paint brush
•
Lens opener
(Fabricated from gauge 18 metal sheet.
See Figure 1-E below for details.)
•
Cotton
•
Tissue paper
•
Cotton buds
•
Pointed toothpick
•
70% Ethyl alcohol
All dimensions are in millimeters.
Figure 1-E. Lens Opener
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Problem 1:
There are spots in the viewing field.
Probable Cause:
Dirty eyepiece and/or objective lenses
Solution:
Clean the eyepiece and objective lenses.
Before cleaning the eyepiece lens, identify if it is coated or not through the reflection in an open area.
Non-coated lens’ reflection is non-colored while the coated lens’ reflection is colored.
Procedure:
1. Cleaning the eyepiece lens.
Clean the eyepiece lens first since this part can be easily contaminated. After cleaning, you can use
this to magnify defects when inspecting the other parts of the microscope.
Eye
Object
Eyepiece lens
Figure 1-F. Using the eyepiece lens as magnifier
Usually, the eyepiece has two lenses as shown in Figure 1-I. The exposed surface is more likely to
get stained, thus, it needs to be cleaned more often than the inner surface. Just wipe the outer
surface with cotton buds moistened with a small amount of alcohol. If you can still see stains, you
should open the eyepiece and clean the inner surface of the lenses.
Exposed surface
Inner surface
Exposed surface
Figure 1-G. Cross-section of the eyepiece
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To open the eyepiece:
Figure 1-H. Opening the eyepiece
To clean, gently wipe the surfaces of the upper and lower lenses using cotton buds moistened with
a small amount of ethyl alcohol. Wipe from the center towards the edges in a circular motion (a).
If you want to clean the edge designated by the red arrow (b), you can use pointed toothpicks
covered with tissue paper or cotton (c).
a
b
c
Figure 1-I. Cleaning the eyepiece lenses
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2. Cleaning the objective lens.
Check the objective lens for dirt and growth of fungus. Using the cleaned eyepiece as magnifier,
you can see the outer surface of the objective lens.
Clean Eyepiece
Figure 1-J. Checking for dirt and
fungus on the objective lens
Objective
Objective lenses usually consist of more than two components; the lenses are smaller and more
complex than the eyepiece lens. So when you open the objective lenses, you should take note of
the sequence and correct position of the parts by placing the components in array. As a rule, the
first component to be removed is the last to be replaced; the last to be detached is the first to be
restored.
1
2
4
3
4X
1
2
3
4
5
10X
1
2
3
4
5
6
40X
Figure 1-K. Disassembled objectives showing the correct
sequence of parts
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A lens opener is needed to open the objectives.
a. If the lock ring is near the opening,
use short type lens opener.
b. If the lock ring is far from the opening,
use long type lens opener.
Figure 1-L. Removing the lock rings
After you open the objective lens, wipe the inner and outer surfaces of the lens using cotton buds
moistened with a small amount of ethyl alcohol.
Figure 1-M. Cleaning objective lenses
Problem 2:
Image is dark.
Probable Cause:
Dirt or defects in the mirror.
Solution:
Clean the mirror.
Most microscopes have a mirror. The mirror reflects light from the sun or from a lamp. It is important
to regularly clean this part for the microscope to function efficiently.
Procedure:
1. Cleaning the mirror.
Wipe the surface of the mirror with soft tissue paper or cloth. If the stain is heavy, moisten the
tissue paper or cloth with a small amount of ethyl alcohol. Do not scrape the dirt or stain using
hard materials for these might scratch the mirror surface.
Figure 1-N. Cleaning the mirror
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Problem 3:
Defective coarse adjustment knob
Probable Cause:
Loose rack and pinion gear assembly
Solution:
Adjust the tightness of the rack and pinion gear assembly.
Procedure:
1. Turn the coarse adjustment knob counterclockwise
until the barrel separates from the arm (a). Remove
the screws (b).
a
REMOVE
c
b
Figure 1-O. Removing the barrel and rack
2. Make a spacer using thin aluminum sheet like the ones obtained from softdrink cans (a). Vary the
thickness of the sheet to get the required clearance between the pinion gear and rack. Put the
spacer as illustrated in the picture below. Replace the rack atop the spacer (b).Tighten the screws
you removed earlier.
a
b
Figure 1-P. Placing a spacer
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Problem 4:
Defective fine adjustment knob.
Probable Cause:
Some parts inside the mechanism need adjustment.
Solution:
Check and adjust the parts.
Procedure:
1. Turn the coarse adjustment knob counterclockwise until the barrel separates from the rest of the
microscope (See Figure 1-O on page 64).
2. Remove two screws. The coarse adjustment mechanism will be detached.
REMOVE
Figure 1-Q. Removing the coarse adjustment mechanism
3. Remove the cover by removing two screws (a). Upon removal of the cover, a dovetail-shaped
attachment with spring (b) will be visible. To view the fine adjustment mechanism, remove the
dovetail-shaped mechanism (c). Make sure that the spring is not lost during removal. If the spring
is lost, it should be replaced.
SPRING
REMOVE
a
b
c
Figure 1-R. Opening the fine adjustment mechanism
4. Sometimes, the small bolt (1) is too tight (see Figure 1-S). Use a screwdriver in unscrewing the
small bolt. The “linkage” (2) should move when the fine adjustment knob is turned.
Figure 1-S. Fine adjustment mechanism
2
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